Method of making free rosin emulsions



Patented May 15, 1934 UNITED STATES METHOD OF MAKING FREE ROSINEMULSIONS Judson A. De Cew, Mount Vernon, N. Y.-

No Drawing. Application November 24, 1931, Serial No. 577,149

4 Claims.

Rosin soap emulsions containing free rosin have always been made bymaking a rosin soap by partial saponification and in the form of aconcentrated aqueous product containing over solids.

This product when required for use is made into a dilute emulsion bypassing the hot soap or size through an emulsifying device with water orsteam or both, as disclosed in many patents, and also methods well knownin the art.

These rosin soaps are generally made from rosin and sodium carbonateNaCos, this alkali being better suited in this boiling process than astronger alkali because it reacts slowly giving ofif the acid gas CO2during the boiling operation and does not carry the saponiiication tosuch a degree as to solidify the product during the boiling process.

It is the purpose of this invention to prepare direct from the rosin adilute rosin soap containing free rosin, so that the emulsifying systemcan be eliminated and the size can be made in the mill in a dilutecondition all ready to use.

This is accomplished by dissolving the rosin directly in a large volumeof water containing a suflicient amount of caustic alkali to produce thekind of free rosin size desired when all of the rosin is dissolved.

I am aware that a dilute rosin soap containing no free rosin has beenmade with cold dilute caustic alkali by a continuous process. It isevident that a cold dilute caustic solution will not produce a freerosin size as the rate of solution is very slow so that it will containfree alkali instead of free rosin.

In order to have accurate control of the composition I use the batchsystem and I accelerate the reaction by heat so that the alkali will notonly dissolve the amount of rosin acids to neutralize the alkali but thesoap formed will also dissolve an additional amount of rosin even in itsdilute state so that a free rosin emulsion is produced in one operation.

My method of operation is to fill a tank, hav ing an agitator of somekind, with hot water having a temperature of from 120 to 180 F., and addto this water while it is being agitated both the caustic alkali andcrushed rosin. As these materials are added to the hot water the rosindissolves in the alkali and in 'the soap formed until an opalescent ormilky emulsion is formed on cooling. In this way a dilute sizecontaining as high as 50% free rosin can be formed.

In making a rosin size with a hot dilute caustic solution a Wider rangeof concentration of alkali is possible than with a cold solution becausethe soap formed doesnot salt out of the hot solution as it -does With acold one. This range, however, has its limitations as far as strength isconcerned, for if the caustic alkali is over 6% NaOI-I it will make asize about 50% solids and this always jells in the tank from oversaponification so that it cannot be circulated or mixed or handled in acommercial manner. It is necessary for safety of operation that thestrength of the alkali be under 4% NaOI-I but inasmuch as it isdesirable to use the soap at a concentration of under 10% and as thestronger the alkali the darker the size for a given temperature, it ismuch better practice to use alkali of about 1% NaOH or less. When it isdesired to have a very light colored size the dilution is extreme.

This process may be carried out continuously by adding a stream ofcrushed rosin to a stream of hot dilute caustic soda and allowing thismixture to flow through a pipe or into a tank in which the right amountof saponification may take place. The temperature of the solution can becontrolled to suit the time of saponification.

The advantages of this process of making rosin size emulsions in oneoperation are-many as all of the apparatus required is a tank withagitation or pump circulation and feeding devices, and by using hotcaustic soda instead of sodium carbonate, there is practically nofrothing during the saponification and all of the disadvantages ofmaking a concentrated size with caustic alkali are avoided, such asjelling and discoloration.

It has not heretofore been known in the art that a high free rosin sizeemulsion can be made by direct saponification of rosin in a highlydiluted caustic alkali. And it has always been considered necessary tofirst make a concentrated soap, which would act as a solvent for morerosin, and which required special equipment tomake into a good emulsion.This fact is proven by many patents that have been issued on the methodsof emulsifying a free rosin size.

In practice, I would use a hot aqueous solution of caustic sodacontaining lb. NaOI-l to 100 lbs. of water to make a free rosin emulsionof about 3% rosin size, or a solution containing Z2 lb. NaOI-I per 100lbs. of Water would make a 6% solution of size which could be furtherdiluted after saponification to a concentration of 2% by adding coldwater. Since the object of this invention is to produce a sizecontaining free rosin, it is necessary to use proportions of rosin andcaustic soda in which the caustic soda is less than 12% of the weight ofthe rosin because this proportion will completely saponify the rosin.All proportions less than 12% will therefore produce a free rosin size.Any quantity of rosin can be used depending upon the free rosin desiredin the emulsion.

One advantage in making a rosin size by the use of caustic soda insteadof soda ash is the fact that the finished size never contains dissolvedbicarbonates or CO2 in solution, which make the solutions unstable, andwhich are always present in a size with sodium bicarbonate.

The advantage of using a dilute solution and at moderate temperatures isthat saponification takes place without polymerization of the rosin anddiscolorization of the size.

I claim:

1. The method of making rosin size emulsion containing free rosin whichcomprises blending rosin and caustic soda in hot water between 120 and180 F. to form a dilute emulsion, the caustic soda used being less than4 percent of the water used and less than 12 percent of the rosin used.2. The method of making a dilute solution of rosin size containing freerosin which consists in mixing rosin and caustic soda wherein thecaustic soda has less than 4 percent NaOH in hot water whose temperaturelies between 120 and 180 F. and stirring the mixture until the requiredamount of rosin is dissolved.

3. The method of making a dilute solution of free rosin size whichcomprises mixing rosin, caustic soda and water under the conditionswherein one-quarter of a pound of caustic is used to 100 pounds of waterand the caustic is less than 12 percent of the weight of the rosin, andthe temperature of the water lies between 120 F. and 180 F., to producean emulsion having about 3 percent rosin size.

4. The method of making a dilute solution of free rosin size whichcomprises mixing rosin, caustic soda and water under the conditionswherein one-half of a pound of caustic is used to 100 pounds of waterand the caustic is less than 12 percent of the weight of the rosin, andthe temperature of the water lies between 120 F. and 180 F., to producean emulsion having about 6 percent rosin size.

JUDSON A. DE CEW.

